1. Field of the Invention
The present invention relates to an endoscopic high-frequency snare for mucosal resection, and the like, via a passage of electric current through the snare, which is used by being introduced into a body through a treatment tool insertion channel of an endoscope.
2. Description of the Related Art
A typical endoscopic high-frequency snare is provided with an insulating flexible sheath, a conductive control wire which is inserted into the flexible sheath to be freely movable therein along the axis of the flexible sheath, and a snare loop made of a resilient wire which is fixed to the distal end of the control wire. The snare loop moves in and out of the distal end of the flexible sheath when the control wire is operated to retract and advance in the flexible sheath, respectively. The snare loop expands by its resiliency when positioned outside the flexible sheath, and becomes narrow when retracted into the flexible sheath. This type of endoscopic high-frequency snare is disclosed in, e.g., Japanese Patent Application Laid-open No.2000-83963.
In a typical endoscopic surgical operation for removing mucosa with an endoscopic high-frequency snare, firstly a mark or marks for indicating the area of a target affected part which is to be removed are made on a surface of the mucosa on the outline of the target affected part, subsequently the surface of the mucosa is dissected annularly along the mark or marks, and thereafter the target affected part of the mucosa surrounded by the annular cut is excised.
Among these three procedures, any conventional endoscopic high-frequency snare alone can perform only the procedure of excising mucosa such as the aforementioned target affected part of the mucosa surrounded by the annular cut. Namely, in addition to an endoscopic high-frequency snare, it is necessary to prepare a special marking tool, and another tool for dissecting mucosa. Therefore, each treatment tools, i.e., the endoscopic high-frequency snare, the marking tool and the dissecting tool, must be interchanged with another treatment tool thereof in order to be used, which makes the endoscopic surgical operation troublesome and complicated, and raises the possibility of contaminated water being scattered each time such treatment tools are interchanged; moreover, the disinfecting operation for the treatment tools becomes troublesome.
To prevent this problem from occurring, if the resilient wire that forms the snare loop is provided at a distal end of the resilient wire with a hook portion, which is formed by bending a portion of the resilient wire in the vicinity of the distal end thereof so that the hook portion projects in a lateral direction of the snare loop, both the aforementioned marking and mucosa dissection procedures can be carried out with the hook portion before the aforementioned mucosa excision procedure with the snare loop.
However, if such a hook portion is formed simply by bending a portion of the resilient wire of the snare loop laterally in the vicinity of the distal end thereof, there is a possibility of the hook portion largely protruding in a lateral direction (radial direction) of the flexible sheath from the distal end of the flexible sheath to such an extend as to get caught by an inner peripheral surface of a channel (e.g., treatment tool insertion channel) of an endoscope, thus making it difficult for the endoscopic high-frequency snare to travel in the channel or damaging the snare loop, when the endoscopic high-frequency snare is inserted and withdrawn into and from the channel.